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Fun with Implicit Conversion and Table Partitioning

Rod Edwards takes us through an issue:

CONVERT_IMPLICIT(nvarchar(200),[xxxxxxxxxxxxxxxxxxx].[Category,0)=[@Category] AND CONVERT_IMPLICIT(nvarchar(200),[xxxxxxxxxxxxxxxxxxx].[Id],0)=[@Id]

Oh dear, what’s all that then, we have a fat Residual Predicate, where SQL is performing an Implicit conversion on our query predicates.

Time to look at our datatypes.

This is one of several reasons why I espouse the philosophy of NVARCHAR Everywhere. You can’t have implicit conversion if you’re always using NVARCHAR over VARCHAR.

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